A homolog of human C-reactive protein (CRP) and amyloid Pcomponent (AP) is present in the Syrian hamster as a sex limited serum protein called female protein (FP). FP functionally is similar to both human proteins as it has a Ca++ dependent phosphorylcholine binding site like CRP and is a component of amyloid similar to AP. This protein is a glycoprotein and its synthesis in the liver is controlled by sex hormones and acute phase mediators. Inflammatory results in decreased synthesis of FP in females, whereas increased synthesis of FP is found in males. This divergent acute phase response is controlled by levels of testosterone and estrogen in the injured hamster. FP is a noncovalently assembled pentamer of 30K dalton subunits. The monomer subunits are hydrophilic and can reassemble to form a pentamer indistinguishable from the parent molecule.